Electric automatic deviation correction system of

The electrical automatic deviation correction system of long-span gantry crane

1. The problem is raised

the gantry crane with a long span of more than 40 meters is actually used due to the influence of many factors, such as the difference of running resistance caused by the height and parallel deviation of the crane track, the deviation of the walking wheel diameter, the deviation of the motor speed, and the speed difference between rigid and flexible legs after running for a period of time. Usually, when the deviation is close to 3/1000 of the span, The crane should slow down automatically to correct the deviation, and the driver can also correct the deviation manually according to the deviation indicator; When the deviation exceeds 3/1000 of the span, the deflection limiter will automatically disconnect the crane operation control circuit to make the crane stop automatically

second, the commonly used electrical automatic deviation correction method

to automatically correct the deviation of large-span gantry crane, first analyze the causes and phenomena of the deviation, and then take corresponding deviation correction measures. There are usually the following electrical automatic deviation correction methods:

1. When the speed of the motors on both sides of the rigid leg and the flexible leg is different, for example, the average speed of the motor on the rigid leg side is 1/1000 faster than that on the flexible leg side, which can be corrected by calculating the number of pulses input into the PLC by the pulse encoder

2. The included angle between the main beam and the flexible leg is greater than or less than 90 degrees, which can be corrected by the angular displacement sensor installed on the top of the flexible leg

3. By comparing the actual running linear speed of the rigid leg side cart wheel and the flexible leg side cart wheel, this can be corrected by the closed-loop control method of the rubber friction wheel belt rotary encoder with symptoms: the lower collet is insensitive to rise and fall

4. Install some sensing points directly beside the crane running rail on the rigid leg side and the flexible leg side in parallel, and use the proximity switch to measure the sequence of the proximity switch action on the rigid leg side and the flexible leg side and input it into the PLC input end to correct the deviation

third, the electrical control and automatic deviation correction system of the crane

this scheme adopts the motor on the rigid and flexible leg sides to be driven simultaneously by two frequency converters, and the above method 4 is used for automatic deviation correction control. The specific design instructions of the crane electrical control system are as follows:

1, and the speed regulation ratio of the crane mechanism is about 1:10; The speed of one to five speeds is set as the fastest speed of 10%, 30%, 50%, 75% and 100% (see the general mechanical drawing for the specific range of operating speed)

2, the control mode is the master control of the left box linkage console; The left horizontal mechanism controls the left and right 5 speeds of the crane

3, two pulse encoders should be added to the crane motor, one on each side of the rigid and flexible legs

4, feed back the PGA and PGB pulse signals of the electric but rigid crane on the rigid and flexible leg side to the frequency converter for closed-loop control

5, put forward the speed pulse +01-s0a/s0b, +02-s0a/s0b pulse signals of the waste asphalt mixture thermal regeneration process according to the actual records near the rigid and flexible leg rails, and send them to the PLC input terminals x17 and X20

6, the electrical system adopts a variety of protection functions, including motor overload protection, inverter overload protection, electrical overvoltage and voltage loss protection, phase loss protection, motor overspeed and stall protection, braking unit overheating protection, threshold switch, trolley and trolley limit, and other interlocking protection, line overload, short circuit, open circuit protection, pulse encoder disconnection protection, etc

7, the control system has anti-interference ability, and has shielding and filtering functions for electromagnetic wave radiation, electric voltage instantaneous fluctuations, radio waves, and high-order harmonics of the power supply. The control system can still work normally when the electric voltage fluctuates by 10%

8, four 11kw crane motors at the front flexible leg side, cimr-g7a4055+pgb2 for frequency converter, 4030b for braking unit, Yaskawa, Japan

9, four 11kw crane motors at the rear rigid leg side, cimr-g7a4055+pgb2 for frequency converter, 4030b for braking unit, Yaskawa, Japan

10, the crane discharge resistor adopts zx25s/2h-x resistor, two sets, a total of 8 boxes

fourth, the principle of automatic electrical deviation correction

1. The basic programming and parameter setting method is to calculate the actual running distance of the crane walking wheel on the rigid (flexible) leg side through the speed pulse - use the high-performance proximity switch to record the number of induction nuts on the fixed bolts on the crane rail pressing plate to determine (of course, accurate calculation can place some electromagnetic induction points equidistant beside the crane rigid and flexible leg rails)

2, set the actual running speed of the side of the proximity switch that first sends the pulse to be fast. This pulse signal is immediately input into PLC x17 (or X20), and the speed is recorded immediately and the automatic deviation correction control is carried out

3, the method of automatic deviation correction is to slow down as soon as it is fast - for example, during the operation of the crane, the flexible leg side proximity switch first senses the induction nut on the bolt, and the control end of the flexible leg proximity switch is changed from normally open to normally closed by a non-profit technology company called "the ocean cleanup" designed by the system for handling the largest garbage belt in the Pacific Ocean, so that relay K510 is pulled in, The PLC input terminal X20 generates input signals, which can be programmed: LD X20, ani x17, out y17. At this time, the control terminal s9b of the flexible leg frequency converter inputs the deceleration control signal, and the four motors on the flexible leg side immediately decelerate. When the proximity switch on the rigid leg side also detects the induction nut of the bolt, it automatically disconnects the input signal of s9b, making the motors on the flexible and rigid leg sides operate stably at the same speed at the same time

4, if the crane is in operation, the rigid leg side is fast, the rigid leg side proximity switch first senses the nut on the bolt, and the control end of the rigid leg proximity switch changes from normally open to normally closed, so that the relay k509 is pulled in, and the PLC input end x17 generates an input signal, which can be programmed: LD x17, ani X20, out Y16. At this time, the control end S9 of the rigid leg frequency converter inputs a deceleration control signal, and the four motors on the rigid leg side immediately decelerate, When the proximity switch at the flexible leg side also detects the nut on the bolt, it automatically disconnects the input signal of S9, so that the motors at the rigid and flexible leg sides can operate stably at the same speed at the same time